1. Field of the Invention
The invention relates generally to the field of assay reagents and their use in diagnostic assays. More particularly, the present invention relates to unit-of-use lyophilized reagent compositions, which are especially advantageous in diagnostic assays.
2. Description of Related Art
Various analytical procedures are commonly used in diagnostic assays to determine the presence and/or amount of substances of interest or clinical significance in test samples, such as body fluids. These clinically significant or interesting substances are commonly referred to as analytes. Diagnostic assays have become an indispensable means for detecting analytes in test samples by using the mutual reaction between the analyte and a specific binding member, as typified by the immunoreaction between an antigen and an antibody to that antigen.
Commercially available test devices for performing specific binding assays are usually in the form of test kits comprising packaged combinations of containers holding individual solutions of the reagents necessary for carrying out the assay. To perform the desired assay technique, aliquots of such reagent solutions must be manually or instrumentally dispensed into a reaction vessel with the test sample. If manually dispensed, the assay requires the time and skill of a technician, and if instrumentally dispensed, the assay requires the expense and maintenance of a dispensing apparatus.
Reagent impregnated solid phase test devices have been developed for specific binding assays to overcome the need for reagent measurements and the dispensing of individual reagents. Commonly used solid phase devices of this type include dipsticks, test strips, vials and flow-through devices wherein most or all of the necessary reagents are incorporated within the solid phase material. The assay reagents are generally applied to and dried upon the solid phase material to form reactive sites.
Dipstick devices generally involve a plastic strip with a reagent-containing matrix layered thereon. Typically, a test sample is applied to the device, and the presence of analyte is indicated by a reaction in the matrix layer between the analyte and assay reagent which produces a visually detectable signal such as color-formation. Hochstrasser (U.S. Pat. 4,059,407) discloses a dipstick device which is immersed in a biological fluid to detect analyte in the fluid. Also of interest in the area of dipstick devices are U.S. Pat. Nos. 3,802,842; 3,915,639 and 4,689,309 and WO Application No. 8,600,670.
Test strip devices are exemplified by the devices of Deutsch et al. which involve chromatographic test strips (U.S. Pat. Nos. 4,094,647, 4,235,601 and 4,361,537). The typical device comprises a material capable of transporting a solution by capillary action, i.e., wicking. Different areas or zones along the strip contain the assay reagents needed to produce a detectable signal upon the transport of analyte to or through such zones. The device is suited for both chemical assays and binding assays which are typified by the binding reaction between an antigen and complementary antibody. Many variations on the Deutsch device have been disclosed. Also of interest in the area of test strips are U.S. Pat.
Nos. 4,168,146; 4,298,688; 4,435,504; 4,461,829; 4,517,288 and 4,740,468; European Patent Office Publication Nos. 88,636; 259,157; and 267,006; and German Patent No. 3,445,816.
Flow-through devices generally involve a porous material incorporated with an immobilized assay reagent. Test sample is applied to and flows through the porous material, and analyte in the sample reacts with the reagent to produce an immobilized complex that can then be detected on the porous material. Tom et al. (U.S. Pat. Nos. 4,366,241) disclose a bibulous material with an immunosorbing zone containing an immobilized analyte-specific antibody to which the test sample is directly applied. Other flow-through devices are described in U.S. Pat. Nos. 3,825,410; 3,888,629; 4,446,232; 4,587,102; 4,632,901; 4,637,978 and 4,727,019 and European Patent Office Publication Nos. 212,603; 217,403 and 249,851.
Previously known binding assay devices are generally considered difficult to manufacture. Typically, the reagents are applied individually to the solid phase to form reactive sites with drying of the solid phase after each addition, i.e., the manufacturer must supply the measuring and dispensing skills required by the assays. The dipstick, test strip and flow-through devices also are complicated because the chemical or physical reactions take place in the solid phase as the test sample passes through or migrates along the solid phase, and therefore, the solid phase must be designed to allow appropriate incubation and reaction times between each reactive site. In addition, when such devices are constructed they must be incorporated with the reagents specific for the analyte to be detected. This results in the need to change production techniques for each analyte of interest. Moreover, the reagents incorporated by direct application to and drying upon the solid phase a subject to changes in stability during the storage of the device.